RCBO Tripping

[ban-all-sheds]

Probably not.

An old pole transformer would be though, and gets you within tweaking distance of your T/E breakdown voltage

 

[JohnW2]

Probably not.

Indeed. The wire of the winding is probably only protected with a few microns of varnish.

An old pole transformer would be though, and gets you within tweaking distance of your T/E breakdown voltage

A bit on the bulky side! As I said before, a line output transformer from an old CRT TV would be worth considering (or, indeed, the whole TV!).

Kind Regards, John

 

[ban-all-sheds]

Or a car ignition coil.

As long as whatever you use can be repurposed in a Jacobs Ladder....

 

[JohnW2]

Or a car ignition coil.

They were not really designed to have an AC feed and might well draw a lot from a continuous AC source - but I guess one could cautiously try to feed very low (intially well under 12V) AC into it and see what happened.

Kind Regards, John.

 

[ban-all-sheds]

Or you could use a timer/oscillator and some power transistors to switch the output of a bench power supply, or indeed a 12V battery.

Or in the same scrapyard you get your coil, get a distributor and rig up a handle to it to rotate it by hand....

 

[JohnW2]

Or you could use a timer/oscillator and some power transistors to switch the output of a bench power supply, or indeed a 12V battery.....Or in the same scrapyard you get your coil, get a distributor and rig up a handle to it to rotate it by hand....

Yep, but for Peet's purpose, he would really want a constant (and variable/controllable) HV output, not a series of very brief pulses, wouldn't he? As I implied before, if a way of varying the voltage could be built in, a CRT TV might well do the job.

Kind Regards, John

 

[ban-all-sheds]

I've lost track of what his purpose was...

And anyway - IR testers only give you one pulse.

 

[martinxxxxxx]

It was to establish the breakdown point of t and e.
I remember being told never to IR T&E at 1000VDC, but cannot remember who it was that told me - some lecturer or other I expect - some of them do have their own peccadilloes on what is acceptable in electrical installation and testing. I have looked and looked but cannot find anything concrete to back that assertion

 

[bernardgreen]

I've lost track of what his purpose was...

And anyway - IR testers only give you one pulse.

Which is why testing the IR of electronic equipment is often called flash testing.

 

[martinxxxxxx]

I've lost track of what his purpose was...

And anyway - IR testers only give you one pulse.

Which is why testing the IR of electronic equipment is often called flash testing.

I thought flash testing was slightly different than the IR testing done by modern pat testers and not really part of Pat testing anymore?

as in (from http://www.pattesters.co.uk/pat-testing-faqs/do-i-need-to-flash-pat-test)

Flash Testing or “High potential dielectric strength testing” is a high voltage Insulation test typically 1500 Volts AC for a Class I or 3000 Volts AC for a Class II and was common in PAT testing up until the IEE Code of Practice 2nd edition was published in 2001. On page 27, paragraph 10.4 it said “Dielectric strength testing is not normally carried out during in-service testing. This is normally carried out by the manufacturer on a complete appliance after assembly”. Page 48 paragraph 10.5 of the new Code of Practice 3rd edition also re-states this; thus flash testing is not normally done now.

 

[JohnW2]

I remember being told never to IR T&E at 1000VDC, but cannot remember who it was that told me - some lecturer or other I expect - some of them do have their own peccadilloes on what is acceptable in electrical installation and testing. I have looked and looked but cannot find anything concrete to back that assertion

I can think of some reasons why such advice might be given, mainly in terms of 'responsibility' for any damage done. If regulations and practices do not require testing above 500V, then an electrician who undertook testing at voltages higher than that (and considerably higher than the 'rated' voltages of both cable and accessories) could then be considered responsible for the recification of any damage which resulted. Although theoretical considerations suggest that both T&E and accesories should, if 'perfect', easily cope with 1000V (probably at least 5000V, or more), imperfections in manufacture could result in lower breakdown voltages - but still totally compliant with the rated 'spec', so quite legitimate for sale and use.

Kind Regards, John

 

[JohnW2]

I've lost track of what his purpose was...And anyway - IR testers only give you one pulse.

Which is why testing the IR of electronic equipment is often called flash testing.

As Martin has said, I think 'Flash Testing' actually refers to something rather different, and I'm also unsure about this assertion that 'IR testing only gives you one pulse'.

I agree that, unlike measuring resistance with a multimeter, IR testers don't apply the test voltage 'indefinitely'. My recent experience is only of MFTs (rather than standalone IR testers, like the 'wind-up Meggers' I was brought up on) but the general rule for most measurements with them (apart, IIRC, from voltage) is that they just 'undertake the test' for as long as necessary and then display a 'frozen' result - not the least so as to preserve batteries, and in some cases because of safety, thermal considerations etc. When measuring IR, the instructions for my Fluke MFT say that, after pressing the 'Test' button, one should wait 'until the result is stable and the bleeper has sounded' before noting the result and, in practice, it can take 'a second or three' for that to happen. Whilst some may call that 'second or three' a 'pulse', it is a totally different concept from the series of ('true') pulses, each of perhaps a few msec duration, that one would get from a car ignition system, per BAS's suggestion.

Kind Regards, John

 

[Peet]

I've lost track of what his purpose was...

And anyway - IR testers only give you one pulse.

Which is why testing the IR of electronic equipment is often called flash testing.

The couple of older IR testers I've metered for voltage kept the output volts there for as long as your finger was on the button. Is the pulse thing a modern development?

I was wanting to see what happens to T&E at those kinds of test voltages with a spread of different wire (new, not so new, 30 year old stuff thats been dragged out of a house, maybe a bit of VIR/lead if I can find it etc etc) and also roughly where do things start to go wrong. ie Where does it start to breakdown. Like John says its likely to be fairly high with modern stuff, well beyond the 1kV range of a standard IR tester. But I was interested to see what and where it did do it. Destroying the stuff is all very nice but there's got to be something educational in too for me. And I thought that would be quite nice to bring it to the group as a bit of background stuff.

Friday I russled up a quick switcher to generate some higher voltages. After rumaging round for anything that was already suitable, it was easier to knock one up. I haven't a LOPT to hand and sometimes they have funny optimisations on them for their original purpose. So using an ETD49 core I wound a boost converter (similar to a car ignition coil) that produced a variable 100-1kv out (1 volt at 6A peak going in). Married it up to a voltage x4 stage to see how things were doing.......and then couldnt find the HT probe I can mess about potting the output down to see what's going on but its getting messy. And when the volts go up further it gets more messy to do that. So until the probe jumps out at me (naturally.... I've put it in a safe place) or I come across a suitable power source, I'll pause that one.

Made me chuckle BAS mentioning Mr PhotonicInduction. The washing machine is hilarious. It'd be great if he'd educate more with the entertainment.
Also reminded me about a friend building a marx generator. 25Kv going in and an estimated 250-300kv off the top. Had a mesh fence round it to contain the discharge. And it still managed to wipe the settings off a TV on the next floor up.

 

[Peet]

I've lost track of what his purpose was...

And anyway - IR testers only give you one pulse.

Which is why testing the IR of electronic equipment is often called flash testing.

I suppose with IR testing especially at 1kV, that in places like cellars, and anywhere else that gases could collect, you'd have to be wary of igniting something from a dodgy contact somewhere. The longer the cable the more stored charge for it found a jumpable gap. The dielectric strength of air seems to be about 3kV/mm

 

[ban-all-sheds]

Destroying the stuff is all very nice but there's got to be something educational in too for me.

And there's nothing wrong with quiche now and then. (Particularly made with diced chorizo and a chopped Scotch Bonnet or two added).

Also reminded me about a friend building a marx generator. 25Kv going in and an estimated 250-300kv off the top. Had a mesh fence round it to contain the discharge. And it still managed to wipe the settings off a TV on the next floor up.